Extract Study was made of the death certificates for all 29,457 children under 15 years of age who died of cancer in the United States during 1960–1966. Congenital defects were greatly underreported, but from the anomalies that were recorded, some new understanding of the relation between oncogenesis and teratogenesis may be derived. On 146 death certificates, Down’s syndrome was listed with leukemia, an 11-fold excess over normal expectation. The peak mortality occurred at two years of age. In the general population, the peak occurs two years later and is due to an increase in the rates for acute lymphocytic leukemia. This study and others indicate that, contrary to popular opinion, myelogenous leukemia is not significantly more common than usual in Down’s syndrome. The association of Wilms’ tumor with aniridia or renal anomalies, unknown when the death certificates were made out, was nevertheless apparent. There were previously unreported cases of leukemia with osteogenesis imperfecta, Marfan’s syndrome, Treacher-Collins syndrome, and Ollier’s syndrome. These cases, and others described in the literature, raise the possibility that certain genetically induced disorders of bone or connective tissue may predispose to leukemia. There were also four new cases of leukemia-lymphoma with immunological abnormality (two with myasthenia gravis; one each with ataxia-telangiectasia and agammaglobulinemia), and two with leukemia and congenital granulocytic abnormalities (one each with agranulocytosis and familial granulomatosis). Other concurrences of possible etiologic significance included two of phenylketonuria and leukemia-lymphoma, three of tetralogy of Fallot and glioma and one of cleidocranial dysostosis and medulloblastoma. Clarification of these relations may come from studies of susceptibility to viral transformation in vitro of skin fibroblasts from children with the anomalies noted above. This study indicates that greater accuracy and completeness in filling out death certificates would greatly aid research and the clinical benefits derived from it. Speculation Although imperfect, diagnoses recorded on death certificates may provide clues to as yet unknown relations between cancer and congenital defects. © International Pediatrics Research Foundation, Inc. 1969. All Rights Reserved.